Many modern engines use composite plastic intake manifolds. They are light and efficient, but heat cycles, age and backfires can cause cracks or warped flanges.
Symptoms
- Rough idle and lean fuel trim codes from a vacuum leak.
- Hissing near the manifold.
- Coolant leaks on manifolds with coolant crossovers.
- Broken runner control components on some designs.
Diagnosis
- Smoke-test the intake to locate leaks.
- Inspect the manifold for cracks at runners, ports and mounting bosses.
- Check that the gasket is not the only problem.
Replacement Tips
- Install new intake manifold gaskets.
- Keep debris out of the ports.
- Tighten bolts in sequence without over-torquing the plastic.
- Relearn idle or clear adaptations where the procedure requires.
Evergreen Parts
Evergreen offers cylinder heads and components identified by engine or vehicle application. Use the Evergreen eCatalog to find the right part, and see where to buy Evergreen through our authorized distributors.
